Experimental stress-strain curves for repeated tensile loading of
 0.276 in (7 mm) diameter prestressing steel wire in the inelastic range
are presented. A mathematical model employing a modified form of the Ramberg-Osgood function is proposed to describe the cyclic stress-strain behaviour of the prestressing steel. The experimental stress-strain
results are subjected to regression analysis in order to obtain empirical expressions for the constants in the Ramberg-Osgood function. The constants are found to depend on the strain imposed in the previous loading run and the characteristics of the monotonic stress-strain curve. The stress- strain curve for monotonic loading, with suitably adjusted origin of coordinates in the case of significant reversed loads, is used to describe the envelope curve which the steel stresses cannot exceed. The proposed cyclic stress-strain model predicted the experimental curves with good accuracy.